/**
 * For jQuery versions less than 3.4.0, this replaces the jQuery.extend
 * function with the one from jQuery 3.4.0, slightly modified (documented
 * below) to be compatible with older jQuery versions and browsers.
 *
 * This provides the Object.prototype pollution vulnerability fix to Drupal
 * installations running older jQuery versions, including the versions shipped
 * with Drupal core and https://www.drupal.org/project/jquery_update.
 *
 * @see https://github.com/jquery/jquery/pull/4333
 */

(function (jQuery) {

// Do not override jQuery.extend() if the jQuery version is already >=3.4.0.
var versionParts = jQuery.fn.jquery.split('.');
var majorVersion = parseInt(versionParts[0]);
var minorVersion = parseInt(versionParts[1]);
var patchVersion = parseInt(versionParts[2]);
var isPreReleaseVersion = (patchVersion.toString() !== versionParts[2]);
if (
  (majorVersion > 3) ||
  (majorVersion === 3 && minorVersion > 4) ||
  (majorVersion === 3 && minorVersion === 4 && patchVersion > 0) ||
  (majorVersion === 3 && minorVersion === 4 && patchVersion === 0 && !isPreReleaseVersion)
) {
  return;
}

/**
 * This is almost verbatim copied from jQuery 3.4.0.
 *
 * Only two minor changes have been made:
 * - The call to isFunction() is changed to jQuery.isFunction().
 * - The two calls to Array.isArray() is changed to jQuery.isArray().
 *
 * The above two changes ensure compatibility with all older jQuery versions
 * (1.4.4 - 3.3.1) and older browser versions (e.g., IE8).
 */
jQuery.extend = jQuery.fn.extend = function() {
  var options, name, src, copy, copyIsArray, clone,
    target = arguments[ 0 ] || {},
    i = 1,
    length = arguments.length,
    deep = false;

  // Handle a deep copy situation
  if ( typeof target === "boolean" ) {
    deep = target;

    // Skip the boolean and the target
    target = arguments[ i ] || {};
    i++;
  }

  // Handle case when target is a string or something (possible in deep copy)
  if ( typeof target !== "object" && !jQuery.isFunction( target ) ) {
    target = {};
  }

  // Extend jQuery itself if only one argument is passed
  if ( i === length ) {
    target = this;
    i--;
  }

  for ( ; i < length; i++ ) {

    // Only deal with non-null/undefined values
    if ( ( options = arguments[ i ] ) != null ) {

      // Extend the base object
      for ( name in options ) {
        copy = options[ name ];

        // Prevent Object.prototype pollution
        // Prevent never-ending loop
        if ( name === "__proto__" || target === copy ) {
          continue;
        }

        // Recurse if we're merging plain objects or arrays
        if ( deep && copy && ( jQuery.isPlainObject( copy ) ||
          ( copyIsArray = jQuery.isArray( copy ) ) ) ) {
          src = target[ name ];

          // Ensure proper type for the source value
          if ( copyIsArray && !jQuery.isArray( src ) ) {
            clone = [];
          } else if ( !copyIsArray && !jQuery.isPlainObject( src ) ) {
            clone = {};
          } else {
            clone = src;
          }
          copyIsArray = false;

          // Never move original objects, clone them
          target[ name ] = jQuery.extend( deep, clone, copy );

          // Don't bring in undefined values
        } else if ( copy !== undefined ) {
          target[ name ] = copy;
        }
      }
    }
  }

  // Return the modified object
  return target;
};

})(jQuery);